CaMKII biophysics and its role in LTP

项目总结 记忆是如何超过编码它的分子的寿命的呢？二十多年前，弗朗西斯 克里克有远见卓识地推测，也许多聚体蛋白质可以通过 通过亚基交换与新合成的蛋白质共享其激活状态，以存储 多年的记忆。钙调素依赖的蛋白激酶II(CaMKII)是一种可以 符合这一描述。例如，CaMKII在其功能关键部位的突变会导致严重的学习 和记忆缺陷。CaMKII以阈值神经元尖峰频率激活，对长期 增强(LTP)。理解LTP的一个主要障碍是缺乏对如何监管 在最初的高频刺激中招募的通路能够在面部保持持续活跃 正在进行的蛋白质周转。我们最近的研究表明，CaMKII亚基在 全酶以依赖于激活的方式。重要的是，激酶活性被赋予未激活的 CaMKII全酶通过亚基交换导致的反式磷酸化，从而增强 激活信号超过了蛋白质降解的时间。这个循环可能会无限期地持续下去。我们的工作是 目的是进一步研究这一现象，特别是关于它在LTP中的作用。我们的主要研究 目标是：1)了解CaMKII独特的生物物理性质的作用(连接子长度如何影响 激活、频率依赖和亚单位交换)，这有助于它成为一种潜在的记忆 分子，和2)研究CaMKII的性质(如亚基交换和基因变化 表达)，以确定其在LTP中的生理作用。这些具有挑战性的目标要求 从分子水平(蛋白质结构和调节)到细胞水平获得的信息的综合 (哺乳动物细胞培养)，最后到动物层面(转基因小鼠)，这将用于未来的研究。 拟议工作的完成将使我们能够更好地处理神经系统疾病的进展，因为它影响 记忆，如阿尔茨海默氏症、痴呆症和创伤性脑损伤的病理。

PROJECT SUMMARY How does a memory outlast the lifetime of the molecule that encodes it? More than two decades ago, Francis Crick had the foresight to speculate that perhaps a multimeric protein could serve as a molecular memory by sharing its activation state with newly synthesized proteins through subunit exchange in order to store a memory for years. Ca2+-calmodulin dependent protein kinase II (CaMKII) was identified as an enzyme that may fit this description. For example, mutation of CaMKII at sites critical for its function results in severe learning and memory defects. CaMKII is activated at a threshold neuronal spike frequency and is crucial to long-term potentiation (LTP). A major obstacle to understanding LTP is the absence of understanding how regulatory pathways recruited during this initial high-frequency stimulus are able to remain persistently active in the face of ongoing protein turnover. Our recent work has shown that CaMKII exchanges subunits between holoenzymes in an activation-dependent manner. Importantly, kinase activity is conferred to unactivated CaMKII holoenzymes by trans-phosphorylation as a consequence of subunit exchange, thereby potentiating the activation signal past the time of protein degradation. This cycle may continue indefinitely. Our work is aimed to further investigate this phenomenon, specifically in respect to its role in LTP. Our major research goals are to: 1) understand the role of the unique biophysical properties of CaMKII (how linker length affects activation, frequency dependence and subunit exchange) that contribute to its potential for being a `memory molecule,' and 2) investigate the properties of CaMKII (such as subunit exchange and changes in gene expression) in cellular systems to determine its physiological role in LTP. These challenging goals require the synthesis of information obtained from the molecular level (protein structure and regulation) to the cellular level (mammalian cell culture) and finally to the animal level (transgenic mice), which will be for future study. Completion of the proposed work will allow us to better address neurologic disease progression as it affects memory, such as pathologies seen in Alzheimer's, dementia, and traumatic brain injury.